In submersible applications, such as in the off-shore industry, cooling of submerged electrical equipment and power consumers is achievable by flushing the equipment with a coolant fluid. The coolant may be a gaseous or liquid fluid that is circulated about the equipment to be cooled, transferring heat energy from the electrical equipment to the sea directly or indirectly through heat exchangers. Operating conditions may include cooling fluid temperatures in the range of 70-160° C., and cooling fluid pressures rising above the ambient seawater pressures.
Electrical power is typically supplied to the submerged electrical application from shore—or surface-based generators via a power cable which is terminated in a pressure-compensated housing of a connector assembly, herein referred to as a penetrator. The penetrator housing is designed in a rear end to receive sealingly the power cable, and is designed in a forward or connecting end to penetrate an enclosure housing the electrical equipment and to connect electrically the power cable conductor with the internal electrical conductor.
In practice, several design parameters have to be considered in a penetrator adapted for conducting power to electric equipment in submersible applications. For example, in electrical applications where a coolant is electrically conductive, such as in the case of a motor flushed with conductive gas or seawater, e.g., the connection between penetrator and motor winding, or a cable spliced to the winding as the case may be, has to be performed in an electrically isolated environment. Another consideration relates to the choice of materials in sealing structures that need to be compatible with the subject coolant fluid. In order to meet these design requirements, penetrators for submersible applications usually need to be modified or adapted for each specific application.
The present invention is applicable to submersible applications in general. For purpose of illustration, a non-limiting example includes a motor application, such as the submerged motor driven pump published as JP 2000-227092. With reference to FIG. 1, a pump motor 13 is disclosed to be arranged in an inner cylinder 11A in a pump casing 1 inside which water is circulated. A lubricating oil is used for cooling a motor shaft seal 21. The oil is contained in an annular chamber 15, separating the inner cylinder 11A from the surrounding pump water. The circumferential continuity of the annular chamber 15 is interrupted by a chamber 16 which adjoins, by an inside face thereof, the exterior of the inner cylinder 11A. The outside of chamber 16 faces the pump water. Electrical equipment housed in chamber 16 is connectable to a power supply via a cable insert port 26 communicating the chamber 16 with the exterior of pump casing 1.
Devices for underwater termination of power cables are previously known, see WO 99/34495, e.g., wherein a device is disclosed comprising connectors arranged for penetration into the enclosure of an underwater power consumer. Each such penetrator comprises power cable termination components enclosed in a penetrator housing extending from a rear end to a forward end of the penetrator, the rear end arranged to seal about the isolation of a power supply cable received in the housing from the rear end, and the forward end exposing a connector arranged for electrically connecting the power consumer to the penetrator. The penetrators are pressure compensated by means of dielectric liquid contained in the penetrator housings.
It is further previously known to effect mating between conductors within a dielectric fluid volume, see e.g. U.S. Pat. No. 3,643,207. A sealed electrical connector is disclosed, comprising a first body part which is mateable with a second body part projecting from the exterior of a bulkhead. Power consumer conductors reach through the bulkhead into a chamber formed in the first body part. The chamber is filled with dielectric fluid such as nonconductive oil, grease or gel. Conductors projecting from the first body part are insertable into the chamber via slits formed in a diaphragm sealing the entrance into the chamber. A compressible boot member, open to the environment and reaching through the chamber, keeps the fluid volume in equilibrium with the ambient pressure.